Precursor Cis Research Articles

Oxidative Addition of MeI to a Rollover Complex of Platinum(II): Isolation of the Kinetic Product

A pair of new Pt(II)/Pt(IV) 2,2′-bipyridine cyclometalated rollover complexes have been synthesized and characterized. [Pt(bpy-H)(CH3)(PMe3)] (1), where bpy-H = κ2N,C-2,2′-bipyridine, was obtained from the electron-rich precursor cis-[Pt(CH3)2(DMSO)2] with a one-pot, two step synthesis; its reactivity has been tested with CH3I, giving the corresponding Pt(IV) complex cis-[Pt(bpy-H)(CH3)2(I)(PMe3)] (2), which was fully characterized. Crystals suitable for X-ray analysis were obtained and allowed the determination of the structure of isomer 2A which is the product of the trans addition of CH3I, usually thought of as the kinetic product.

Novel 3-(Aminomethyl)naphthoquinone Mannich Base-Platinum(IV) Complexes: Synthesis, Characterization, Electrochemical and Cytotoxic Studies

Three novel platinum(IV) complexes cis,cis,trans-[Pt(HL1-3)Cl2(OH)2] 1b-3b (HL = 2-hydroxy-3-[(R1-amino)(pyridin-2-yl)methyl]-1,4-naphthoquinone, R1 = n-butyl, HL1; n-heptyl, HL2 and n-decyl, HL3) have been obtained from the oxidation of the respective precursors cis-[Pt(HL1-3)Cl2] 1a-3a. Cyclic voltammetry studies of 1b-3b in MeCN showed the quasi-reversible naphthoquinonate (NQO-, i.e. , L-) redox process and irreversible process attributed to the reduction of the Pt4+/Pt2+ pair, at potentials about 400 mV less negative than for the cisplatin precursor cis,cis,trans-[Pt(NH3)2Cl2(OH)2]. Hydrogen bond interaction between the naphthoquinone 2-hydroxyl group and an axially coordinated hydroxide ligand in 1b-3b has been proposed to favor the Pt4+/Pt2+ reduction. The cytotoxicity studies against four human cancer cell lines have shown that in general the platinum(IV) and platinum(II)derivatives exhibit the same cytotoxic profile and are all more active than cisplatin. The lowest in vitro IC50 values have been observed for 2b-3b, which bear ligands with the largest R1 groups (HL2-HL3) being the most lipophilic. Furthermore similar IC50 values for platinum(II) and platinum(IV) complexes of the same ligands have been associated with rapid in vitro reduction of the latter complexes to afford 1a-3a.

New half sandwich-type Ru(ii) coordination compounds characterized by the fac-Ru(dmso-S)3 fragment: influence of the face-capping group on the chemical behavior and in vitro anticancer activity

The Ru(II) complex fac-[RuCl(dmso-S)(3)(dmso-O)(2)][PF(6)] (P2) was found to be an excellent precursor for the facile preparation in high yield of half sandwich-type compounds of the general formula fac-[RuCl(dmso-S)(3)(N)(2)][PF(6)] (e.g. (N)(2) = 1,2-diaminoethane (en, 4), trans-1,2-diaminocyclohexane (dach, 5), or 2 NH(3) (6)). Neutral half sandwich-type compounds of the general formula fac-[RuCl(dmso-S)(3)(N-O)] where N-O is an anionic chelating ligand (e.g. N-O = picolinate (pic, 7)) are best prepared from the universal Ru(II)-dmso precursor cis-[RuCl(2)(dmso)(4)] (P1). These complexes, that were fully characterized in solution and in the solid state, are structurally similar to the anticancer organometallic compounds [Ru(η(6)-arene)(chel)Cl][PF(6)](n) but, in place of a face-capping arene, have the fac-Ru(dmso-S)(3) fragment. In contrast to what observed for the corresponding arene compounds, that rapidly hydrolyze the Cl ligand upon dissolution in water, compounds 4-6 are very stable and inert in aqueous solution. Probably their inertness is the reason why they showed no significant cytotoxicity against the MDA-MB-231 cancer cell line.

Ethene Hydromethoxycarbonylation Catalyzed by cis-[Pd(SO 4)(PPh 3) 2]/H 2SO 4/PPh 3

The neutral precursor cis-[Pd(SO 4)(PPh 3) 2] turns into an active catalyst for the hydromethoxycarbonylation of ethene when used in combination with H 2SO 4 and PPh 3. The influence of the following operating conditions on the catalytic activity have been studied: i) H 2SO 4/Pd ratio; ii) PPh 3/Pd ratio; iii) total pressure with CO/ethene = 1/1; iv) pressure of one gas at constant pressure of the other; v) H 2O concentration; vi) temperature. At 100 °C a TOF = 2168 h −1 has been achieved when the catalytic system is used in the ratios Pd/H 2SO 4/P = 1/107/18 (mol/mol), under 6 bar (CO/E = 1/1), H 2O concentration 0.16% in MeOH by weight. After catalysis and upon addition of LiCl, trans-[Pd(COEt)Cl(PPh 3) 2], which is related to the “Pd-H” catalytic cycle, has been isolated. Cis-[Pd(SO 4)(PPh 3) 2] in CD 2Cl 2/MeOH reacts with CO to give a PdCOOMe complex (related to the “carbomethoxy mechanism”), which neither inserts ethene, nor gives methyl propanoate (MP). In the presence of H 2O and H 2SO 4 the carbomethoxy complex is unstable giving a Pd-H complex, which yields catalysis to MP in the presence of CO and ethene. The “Pd-H” and “Pd-COOMe” catalytic cycles are discussed on the basis of the influence of the operating conditions on the TOF and of NMR evidences.

Novel palladium(II) and platinum(II) complexes of biocidal benzisothiazolinone (Bit); X-ray crystal structures of co-crystallised Bit/BitO and cis-Pd(en)(Bit −1H) 2·H 2O

Reaction of benzisothiazolinone (Bit), a well-known biocide, with the Pd(II) and Pt(II) am(m)ine precursors cis-[Pd(en)(H 2O) 2](NO 3) 2 and cis-[Pt(NH 3) 2(H 2O) 2](NO 3) 2 yielded cis-Pd(en)(Bit −1H) 2 and cis-Pt(NH 3) 2(Bit −1H) 2, respectively. Bit is bound to the metal centres in both cases through the deprotonated isothiazolinone N. The crystal structures of a Bit/BitO co-crystal and cis-Pd(en)(Bit −1H) 2·H 2O are also described.

Structural characterization and cytotoxicity studies of ruthenium(II)–dmso–chloro complexes of chalcone and flavone derivatives

A synthetic precursor cis-[Ru IICl 2(dmso) 4] is complexed separately with 3-(4-benzyloxyphenyl)-1-(2-hydroxylphenyl)-prop-2-en-1-one (L 1H) and 2-(4-benzyloxyphenyl)-3hydroxy-chromen-4-one (L 2H). The resulting complexes are assigned the composition fac-[RuCl(S-dmso) 3(L 1)] 1 and fac-[RuCl(S-dmso) 3(L 2)] 2 using elemental analyses, FAB mass data and spectroscopic (IR, 1H NMR, UV–Vis, emission) spectral properties. The X-ray diffraction analysis shows that complexes self-associate through non-covalent interactions and provide 1D and 2D supramolecular structures. These complexes are assayed for their cytotoxicity studies on Dalton Lymphoma cell lines.

Soluble Redox-Active Polymetallic Chains [{Ru0(CO)(L)(bpy)}m]n (bpy = 2,2′-bipyridine, L = PrCN, Cl−; m = 0, −1): Electrosynthesis and Characterization

Electrochemical and spectroelectrochemical techniques were employed to study in detail the formation and so far unreported spectroscopic properties of soluble electroactive molecular chains with nonbridged metal-metal backbones, namely, [{Ru(0)(CO)(PrCN)(bpy)}(m)](n) (m = 0, -1) and [{Ru(0)(CO)(bpy)Cl}(m)](n) (m = -1, -2; bpy = 2,2'-bipyridine). The precursors cis-(Cl)-[Ru(II)(CO)(MeCN)(bpy)Cl(2)] (in PrCN) and mer-[Ru(II)(CO)(bpy)Cl(3)](-) (in tetrahydrofuran (THF) and PrCN) undergo one-electron reductions to reactive radicals [Ru(II)(CO)(MeCN)(bpy(*-))Cl(2)](-) and [Ru(II)(CO)(bpy(*-))Cl(3)](2-), respectively. Both [bpy(*-)]-containing species readily electropolymerize on concomitant dissociation of two chloride ligands and consumption of a second electron. Along this path, mer-to-fac isomerization of the bpy-reduced trichlorido complex (supported by density functional theory calculations) and a concentration-dependent oligomerization process contribute to the complex reactivity pattern. In situ spectroelectrochemistry (IR, UV/vis) has revealed that the charged polymer [{Ru(0)(CO)(bpy)Cl}(-)](n) is stable in THF, but in PrCN it converts readily to [Ru(0)(CO)(PrCN)(bpy)](n). An excess of chloride ions retards this substitution at low temperatures. Both polymetallic chains are completely soluble in the electrolyte solution and can be reduced reversibly to the corresponding [bpy(*-)]-containing species.

Driving forces in substitution reactions of octahedral complexes: The influence of the competitive effect

The reaction of cis-[RuCl 2(P–P)(N–N)] type complexes (P–P = 1,4-bis(diphenylphosphino)butane or (1,1′-diphenylphosphino)ferrocene; N–N = 2,2′-bipyridine or 1,10-phenantroline) with monodentate ligands (L), such as 4-methylpyridine, 4-phenylpyridine and benzonitrile forms [RuCl(L)(P–P)(N–N)] + species. Upon characterization of the isolated compounds by elemental analysis, 31P{ 1H} NMR and X-ray crystallography it was found out that the type of the L ligand determines its position in relation to the phosphorus atom. While pyridine derivatives like 4-methylpyridine and 4-phenylpyridine coordinate trans to the phosphorus atom, the benzonitrile ligand (bzCN), a good π acceptor, coordinates trans to the nitrogen atom. A 31P{ 1H} NMR experiment following the reaction of the precursor cis-[RuCl 2(dppb)(phen)] with the benzonitrile ligand shows that the final position of the entering ligand in the complex is better defined as a consequence of the competitive effect between the phosphorus atom and the cyano-group from the benzonitrile moiety and not by the trans effect. In this case, the benzonitrile group is stabilized trans to one of the nitrogen atoms of the N–N ligand. A differential pulse voltammetry experiment confirms this statement. In both experiments the [RuCl(bzCN)(dppb)(phen)]PF 6 species with the bzCN ligand positioned trans to a phosphorus atom of the dppb ligand was detected as an intermediate complex.

Synthesis, characterization, X-ray structure and in vitro antimycobacterial and antitumoral activities of Ru(II) phosphine/diimine complexes containing the “SpymMe 2” ligand, SpymMe 2 = 4,6-dimethyl-2-mercaptopyrimidine

The reaction of cis-[RuCl 2(dppb)(N–N)], dppb = 1,4-bis(diphenylphosphino)butane, complexes with the ligand HSpymMe 2, 4,6-dimethyl-2-mercaptopyrimidine, yielded the cationic complexes [Ru(SpymMe 2)(dppb)(N–N)]PF 6, N–N = bipy ( 1) and Me-bipy ( 2), bipy = 2,2′-bipyridine and Me-bipy = 4,4′-dimethyl-2,2′-bipyridine, which were characterized by spectroscopic and electrochemical techniques and X-ray crystallography and elemental analysis. Additionally, preliminary in vitro tests for antimycobacterial activity against Mycobacterium tuberculosis H37Rv ATCC 27264 and antitumor activity against the MDA-MB-231 human breast tumor cell line were carried out on the new complexes and also on the precursors cis-[RuCl 2(dppb)(N–N)], N–N = bipy ( 3) and Me-bipy ( 4) and the free ligands dppb, bipy, Me-bipy and SpymMe 2. The minimal inhibitory concentration (MIC) of compounds needed to kill 90% of mycobacterial cells and the IC 50 values for the antitumor activity were determined. Compounds 1– 4 exhibited good in vitro activity against M. tuberculosis, with MIC values ranging between 0.78 and 6.25 μg/mL, compared to the free ligands (MIC of 25 to >50 μg/mL) and the drugs used to treat tuberculosis. Complexes 1 and 2 also showed promising antitumor activity, with IC 50 values of 0.46 ± 0.02 and 0.43 ± 0.08 μM, respectively, against MDA-MB-231 breast tumor cells.

Phosphinic Platinum Complexes with 8-Thiotheophylline Derivatives: Synthesis, Characterization, and Antiproliferative Activity

The platinum mixed-phosphine complexes (SP-4,2)-[PtCl(8-MTT)(PPh3)(PTA)] (2) and cis-[Pt(8-MTT)2(PPh3)(PTA)] (3) (MTTH2 = 8-(methylthio)theophylline, PTA = 1,3,5-triaza-7-phosphaadamantane) have been prepared from the precursor cis-[PtCl2(PPh3)(PTA)] (1), which has been fully characterized by X-ray diffraction determination. Antiproliferative activity tests indicated that the presence of one lipophilic PPh3 and one hydrophilic PTA makes 1-3 more active than the analogues bearing two PPh3 or two PTA. The reactivity of cis-[PtCl2(PPh3)2], cis-[PtCl2(PTA)2], and cis-[PtCl2(PPh3)(PTA)] with the bis(thiopurines) bis(S-8-thiotheophylline)methane (MBTTH2), 1,2-bis(S-8-thiotheophylline)ethane (EBTTH2), and 1,3-bis(S-8-thiotheophylline)propane (PBTTH2) has also been investigated. New binuclear complexes have been prepared and identified by spectroscopic techniques and their antiproliferative activities on T2 and SKOV3 cell lines evaluated.

New nitrosyl ruthenium complex [RuCl(NO)(dcype)(bipy)](PF6)2: Synthesis, electrochemistry, NMR and ESI-MS/MS studies

Reactivity of cis-[RuCl2(dcype)(bipy)] (dcype=1,2-bis(dicyclohexylphosphino)ethane and bipy=2,2′-bipyridine) with nitric oxide afforded the new dicationic complex [RuCl(NO)(dcype)(bipy)]2+. The complex isolated as PF6- salt was characterized by spectroscopical, electrochemical and ESI-MS/MS techniques as well as elemental analysis. Surprisingly the analysis of 31P{1H} and 15N{1H} NMR spectra of the [RuCl(15NO)(dcype)(bipy)]2+ complex reveal that the NO is in trans position to one of the P atom of dcype. The IR spectrum showed the presence of υNO in 1889cm−1 with is in agreement with the presence of NO+, but based on 31P{1H} NMR analysis the nitrosyl do not behave as a strong π-acceptor since little (or none) trans structural effect was observed on 31P chemical shift compared to the precursor cis-[RuCl2(dcype)(bipy)]. In the ESI-MS analysis, we just have detected the intact nitrosyl complex in CH2Cl2 solutions, but in MeOH solutions, the ion [M−NO]+ was detected, indicating the lability of M−NO bond. MSn spectra with variable collision energy indicate a fragmentation pathway with radical bi-cyclohexyl-phosphine and two cyclohexene losses.

New pentafluorophenyl complexes with phosphine-amide ligands

A series of nickel(II) and palladium(II) complexes containing one or two pentafluorophenyl ligands and the phosphino-amides o-Ph 2PC 6H 4CONHR [R = i Pr ( a), Ph ( b)] displaying different coordination modes have been synthesised. The chelating ability of these ligands and the influence of both coligands and the metal centre in their potential hemilabile behaviour have been explored. The crystal structure of ( b) has been determined and reveals N–H⋯O intermolecular hydrogen bonding. Bis-pentafluorophenyl derivatives [M(C 6F 5) 2( o-Ph 2 PC 6H 4C O-NHR)] [M = Ni; R = i Pr ( 1a); R = Ph ( 1b); M = Pd; R = i Pr ( 2a); R = Ph ( 2b)] in which ( a) and ( b) act as rigid P, O-chelating ligands were readily prepared from the labile precursors cis-[M(C 6F 5) 2(PhCN) 2]. X-ray structures of ( 1a), ( 1b) and ( 2a) have been established, allowing an interesting comparative structural discussion. Dinuclear [{Pd(C 6F 5)(tht)(μ-Cl)} 2] reacted with ( a) and ( b) yielding the monopentafluorophenyl complexes [Pd(C 6F 5)Cl{ PPh 2(C 6H 4–C ONH–R)}] (R = i Pr ( 3a), Ph ( 3b)) that showed a P, O-chelating behaviour of the ligands, confirmed by the crystal structure determination of ( 3a). New cationic palladium(II) complexes in which ( a) and ( b) behave as P-monodentate ligands have been synthesised by reacting them with [{Pd(C 6F 5)(tht)(μ-Cl)} 2], stoichiometric Ag(O 3SCF 3) and external chelating reagents such as cod [Pd(C 6F 5)(cod){ PPh 2(C 6H 4-CONH-R)}](O 3SCF 3)(R = i Pr ( 4a), Ph ( 4b)) and 2,2′ -bipy [Pd(C 6F 5)(bipy){ PPh 2(C 6H 4-CONH-R)}](O 3SCF 3) (R = i Pr ( 5a), Ph ( 5b)). When chloride abstraction in [{Pd(C 6F 5)(tht)(μ-Cl)} 2] is promoted by means of a dithioanionic salt as dimethyl dithiophospate in the presence of ( a) or ( b), the corresponding neutral complexes [Pd(C 6F 5){S(S)P(OMe) 2}{ PPh 2(C 6H 4-CONH-R)}] (R = i Pr ( 6a), Ph ( 6b)) were obtained.

Platinum (II) and palladium (II) 1,3,5-triaza-7-phosphaadamantane (PTA) complexes as intramolecular hydroamination catalysts in aqueous and organic media

Complexes of the general formula cis-[MX 2(PTA) 2] (M = Pd, Pt; X = Cl, Br, I; PTA = 1,3,5-triaza-7-phosphaadamantane) were used to study the catalytic intramolecular hydroamination/cyclization of 4-pentyn-1-amine into 2-methyl-pyrroline in water, methanol, and dimethyl sulfoxide (DMSO). Kinetic data were measured via 1H NMR under homogeneous conditions at 50 °C and showed the following trends in rate: (i) Fastest rates were observed in D 2O. (ii) The Pd complexes of this study produced faster rates than the Pt complexes. (iii) The identity of the halide had no effect on the catalytic rate. Cyclization by the catalytic precursor cis-[PdCl 2(PTA) 2] ( 4) in D 2O was zero-order in substrate and first-order in metal complex with Δ H ‡ = 20.0 ± 2.1 kcal/mol, Δ S ‡ = −7.4 ± 6.3 cal/mol K, and E a = 20.6 ± 2.1 kcal/mol. The acetylide complex, trans-[Pt(C C(CH 2) 3NH 2) 2(PTA) 2] ( 6) precipitated from a catalytic mixture involving cis-[PtBr 2(PTA) 2] ( 2). Spectroscopic and kinetic studies indicated that 6 and its cis analog, 7, were the predominant species in solution and that they were both active catalysts for the cyclization reaction. These data, in conjunction with the rate trends, indicated that the mechanism of the Pd(II) and Pt(II) catalyzed hydroamination of terminal alkynylamines in aqueous solution followed a unique mechanism with cyclization of an acetylenic-amine ligand being rate determining.

Mechanistic studies on the formation of Pt(II) hydroformylation catalysts in imidazolium-based ionic liquids

The kinetics of the formation of the active species cis-[Pt II(PPh 3) 2Cl(SnCl 3)] and cis-[Pt II(PPh 3) 2(SnCl 3) 2] from the hydroformylation catalyst precursor cis-[Pt II(PPh 3) 2Cl 2] in the presence of SnCl 2, was studied in two different imidazolium-based ionic liquids. A large range of different chlorostannate melts consisting of 1-butyl-3-methyl-imidazolium cations and [Sn x Cl y ] (− y + 2 x) anions with varying molar fraction of SnCl 2, were prepared and characterized by 1H and 119Sn NMR. The observed chemical shifts point to major changes in the composition of the anionic species within the melt. The second ionic liquid employed, viz., 1-butyl-3-methyl-imidazolium-bis(trifluormethylsulfonyl)amide was prepared in a colorless quality that enabled its application in kinetic studies. The concentration and temperature dependence of the substitution of Cl − by [SnCl 3] − to yield cis-[Pt II(PPh 3) 2Cl(SnCl 3)], could be studied in detail. Theoretical (DFT) calculations were employed to model the reaction progress and to resolve the role of the ionic liquid in the activation of the catalyst. The available results are presented and a plausible mechanism for the formation of the catalytically active species is suggested.

Multinuclear platinum(ii)–amine complexes containing bis(aminopropyl)dicarba-closo-dodecaborane(12) ligands

Treatment of the bridging bidentate 1,Z-bis(aminopropyl)-1,Z-dicarba-closo-dodecaborane(12)(1,Z-bis(aminopropyl)-1,Z-carborane) ligands of the type 1,Z-[H(2)N(CH(2))(3)](2)-1,Z-C(2)B(10)H(10)(L(1), Z= 7, 5) or (L(2), Z= 12, 6) with two equivalents of trans-[PtClI(2)(NH(3))](-), followed by halogen ligand metathesis with AgOTf and HCl((aq)) afforded the novel diplatinum(II)-amine species cis-[[PtCl(2)(NH(3))](2)L(n)](7(n= 1) or 8(n= 2), respectively). Similarly, the reaction of L(1) or L(2) with the labile trans-[PtCl(dmf)(NH(3))(2)](+) afforded trans-[[PtCl(NH(3))(2)](2)L(n)](OTf)(2)(9(n= 1) or 10(n= 2), respectively) in good yield and purity. However, isolation of the analogous 1,2-carborane complexes was not possible owing to decomposition reactions that led to extensive degradation of the carborane cage and reduction of the metal centre. The mixed dinuclear complex [cis-[PtCl(2)(NH(3))]-L(1)-trans-[PtCl(NH(3))(2)]]OTf (19) was prepared by treatment of the Boc-protected amine ligand 1-[(Boc)(2)N(CH(2))(3)]-7-[H(2)N(CH(2))(3)]-1,7-C(2)B(10)H(10)(L(3), 15) with trans-[PtCl(dmf)(NH(3))(2)](+) to yield trans-[PtCl(NH(3))(2)L(3)]OTf (16), followed by acid deprotection of the pendant amine group, complexation with trans-[PtClI(2)(NH(3))](-), and halogen ligand metathesis using AgOTf and HCl((aq)). A novel trinuclear species containing 5 was prepared by the addition of two equivalents of 15 to the labile precursor cis-[Pt(dmf)(2)(NH(3))(2)](2+) followed by acid deprotection of the pendant amine groups. Further complexation with two equivalents of trans-[PtClI(2)(NH(3))](-) followed by halogen ligand metathesis using AgOTf and HCl((aq)) afforded the triplatinum(II)-amine species [cis-[Pt(NH(3))(2)(L(1))(2)]-cis-[PtCl(2)(NH(3))](2)](OTf)(2)(23). Complexes 7-10, 19 and 23 represent the first examples of multinuclear platinum(ii)-amine derivatives containing carborane cages. Preliminary in vitro cytotoxicity studies for selected complexes are also reported.

σ-Acetylide complexes of ruthenium and osmium containing alkynylsilane ligands

The use of the ligands, diethynyldiphenylsilane and 1,3-diethynyltetramethyldisiloxane, in the synthesis of Group 8 metal σ-acetylide mononuclear complexes is demonstrated. New complexes trans-[(dppm) 2ClMCCSi(Ph) 2CCH] (M=Ru 1; Os 2) and trans-[(dppm) 2ClMCCSi(Me) 2–O–Si(Me) 2CCH] (M=Ru, 3; Os, 4) featuring different silyl units were prepared from a mixture of cis-[M(dppm) 2Cl 2] and HCCSi(Ph) 2CCH or HCCSi(Me) 2–O–Si(Me) 2CCH in the presence of NaPF 6 followed by deprotonation with 1,8-diazabicyclo[5.4.0]undec-7-ene. All the new complexes have been fully characterized by FTIR and NMR spectroscopies and fast atom bombardment mass spectrometry. Single-crystal X-ray structures of 1 and 2 confirm that the two diphosphines adopt a trans geometry at the metal centre and one of the terminal ethynyl groups remains intact. Complexes 1– 4 show reversible redox chemistry and their half-wave potentials due to the metal centres are less anodic than those for the starting precursors cis-[M(dppm) 2Cl 2] (M=Ru, Os).

New geometrical and linkage isomers of the Ru(II) precursor cis, cis, trans-RuCl 2(dmso-S) 2(dmso-O)(CO): a spectroscopic and structural investigation

The monocarbonyl Ru(II)–dmso precursor cis, cis, trans-RuCl 2(dmso-S) 2(dmso-O)(CO) ( 1) equilibrates slowly in light protected chloroform solution with two new geometrical isomers of formula cis, cis, cis-RuCl 2(dmso-S) 2(dmso-O)(CO) ( 2) and cis, mer-RuCl 2(dmso-S) 3(CO) ( 3). The three isomers have similar stabilities in solution. In 2 and 3 the three sulfoxides are in a meridional geometry, with the CO ligand coordinated trans to one of the cis chlorides. The new complexes 2 and 3 differ only in the coordination mode of one of the two trans sulfoxides: they are both S-bonded in 3, while one is S-bonded and the other O-bonded in 2. Thus 2 and 3 are linkage isomers of each other. The three isomers 1– 3 are also obtained as a mixture by treatment of cis-RuCl 2(dmso) 4 with CO. The spectroscopic characterization of the new compounds 2 and 3 is reported, together with the X-ray structure of 2. Isomer 2 is the first example of a Ru(II)–CO complex in which coordination through the oxygen atom is found for a dmso that is not trans to CO; isomer 3 is the first example of a Ru(II)–dmso complex featuring three S-bonded dmso ligands with a meridional geometry. Considerations relating the stability of the three isomers to their geometry and to the binding mode of the dmso ligands are reported.

Formation of diphenylphosphanylbutadienyl complexes by insertion of two P-coordinated alkynylphosphanes into a PtbondC6F5 bond: detection of intermediate and reaction products.

The reactions between cis-[M(C(6)F(5))(2)(PPh(2)CtriplebondCR)(2)] (M=Pt, Pd; R=Ph, tBu, Tol 2, 3) or cis-[Pt(C(6)F(5))(2)(PPh(2)CtriplebondCR)(PPh(2)CtriplebondCtBu)] (R=Ph 4, Tol 5) and cis-[Pt(C(6)F(5))(2)(thf)(2)] 1 have been investigated. Whereas [M](PPh(2)CtriplebondCtBu)(2) ([M]=cis-M(C(6)F(5))(2)) is inert towards 1, the analogous reactions starting from [M](PPh(2)CtriplebondCR)(2) or [Pt](PPh(2)CtriplebondCR)(PPh(2)CtriplebondCtBu) (R=Ph, Tol) afford unusual binuclear species [Pt(C(6)F(5))(S)mu-[C(R')dbondC(PPh(2))C(PPh(2))doublebondC(R)(C(6)F(5))]M(C(6)F(5))(2)] (R=R'=Ph, Tol, M=Pt 6 a,c, M=Pd 7 a,c; M=Pt, R'=tBu, R=Ph 8, Tol 9) containing a bis(diphenylphosphanyl)butadienyl bridging ligand formed by an unprecedented sequential insertion reaction of two P-coordinated PPh(2)CtriplebondCR ligands into a PtbondC(6)F(5) bond. Although in solution the presence of coordinated solvent S (S=(thf)(x)(H(2)O)(y)) in 6, 7 is suggested by NMR spectroscopy, X-ray diffraction analyses of different crystals of the mixed complex [Pt(C(6)F(5))mu-[C(tBu)doublebondC(PPh(2))C(PPh(2))doublebondC(Tol)(C(6)F(5))]Pt(C(6)F(5))(2)] 9 unequivocally establish that in the solid state the steric crowding of the new diphenylbutadienyl ligand formed stabilizes an unusual coordinatively unsaturated T-shaped 3-coordinated platinum(II) center. Structure determinations of the mononuclear precursors cis-[Pt(C(6)F(5))(2)(PPh(2)CtriplebondCR)(2)] (R=Ph, tBu, Tol) have been carried out to evaluate the factors affecting the insertion processes. The reactions of the platinum complexes 6 towards neutral ligands (L=CO, py, PPh(2)H, CNtBu) in a 1:1 molar ratio afford related diplatinum derivatives 10-13, whereas treatment with CNtBu (1:2 molar ratio) or 2,2'-bipy (1:1 molar ratio) results in the opening of the chelating ring to give cis,cis-[Pt(C(6)F(5))(L)(2)mu-[1-kappaC(1):2-kappaPP'-C(R)doublebondC(PPh(2))C(PPh(2))doublebondC(R)(C(6)F(5))]Pt(C(6)F(5))(2)] (14, 15). The unsaturated or solvento complexes are unstable in solution evolving firstly, through an unexpected formal 4-1 R (Ph, Tol) migration, to the intermediate diphosphanylbutadienyl isomer derivatives [Pt(C(6)F(5))(S)mu-[C(C(6)F(5))doublebondC(PPh(2))C(PPh(2))doublebondC(R)(2)]M(C(6)F(5))(2)] (16, 18) (X-ray, R=Ph, M=Pt) and, finally, to 1-pentafluorophenyl-2,3-bis(diphenylphosphanyl)naphthalene mononuclear complexes (17, 19) by annulation of a phenyl or tolyl group.

Electrochemical preparation and properties of poly- cis-[{Ru III(L) 2(OH 2)} 2O] 4+ (L=pyrrole-substituted-2,2′-bipyridine) modified electrodes. Their electroinduced transformations into poly- cis-[Ru II(L) 2(H 2O) 2] 2+ and poly- cis-[Ru II(L) 2(CH 3CN) 2] 2+ films

The ruthenium μ-oxo bipyridyl dimer cis-[{Ru III(bpy) 2(OH 2)} 2O] 4+ ( 1) (bpy=2,2′-bipyridine) is a remarkable catalyst for the oxidation of water, chloride ion or organic compounds. Only rare examples of immobilization of such catalysts on electrode surfaces have been reported; all attempts are based on the incorporation of 1 into thin polymeric films. These devices are reputed to have rather poor stability due to the leaching of the complex from the film. In this article, we report the syntheses of [{Ru III(L) 2(OH 2)} 2O] 4+ complexes containing substituted bpy ligands L (L=4-(4-pyrrol-1-yl-butyl)-4′-methyl-2,2′-bipyridine (L 1), complex ( 2) or 4,4′-di- tert-butyl-2,2′-bipyridine (L 2), complex ( 3)) from the corresponding mononuclear aquo precursors cis-[Ru II(L 1) 2(H 2O) 2] 2+ ( 4) and cis-[Ru II(L 2) 2(H 2O) 2] 2+ ( 5). Stable functionalized polypyrrole modified electrodes containing the 2-core are obtained by anodic electropolymerization of solutions of 2 in the aprotic non-coordinating solvent CH 2Cl 2. Their electrochemical behavior in aqueous media at several pH values is studied. Some examples of electroinduced transformations occurring within the polymeric films leading to the tailoring of modified electrodes of poly- 4 and cis-[Ru II(L 1) 2(CH 3CN) 2] 2+ are also reported.

Synthesis and characterization of heteroleptic Cr(diimine) 3 3+ complexes

A versatile synthetic procedure is described for the synthesis of previously unreported heteroleptic Cr(diimine) 3 3+ complexes . The method takes advantage of the excellent leaving group characteristics of the trifluoromethanesulfonate (triflate) ligand, CF 3SO 3 − , and involves refluxing a precursor cis-[Cr(diimine) 2(CF 3SO 3) 2]CF 3SO 3 complex with an alternative free diimine ligand in a non-coordinating solvent such as CH 2Cl 2 or CH 3CN. The synthesis and characterization of the heteroleptic systems Cr(phen) 2(bpy) 3+, Cr((phen)(bpy) 2 3+ , Cr(phen) 2(TMP) 3+, Cr(phen)(TMP) 2 3+ , and Cr(phen) 2(DPPZ) 3+ are reported (where phen=1,10-phenanthroline, bpy=2,2′-bipyridine, TMP=3,4,7,8-1,10-phenanthroline, and DPPZ=dipyridophenazine). Capillary electrophoresis studies have proven an especially valuable aid in determining the presence or absence of diimine ligand scrambling (and for establishing purity in general). With the exception of Cr(phen)(bpy) 2 3+ , these syntheses proceed with essentially no diimine ligand scrambling, even when carried out in the presence of excess entering diimine. UV–Vis absorption and emission spectra, and excited state lifetime and cyclic voltammetry data are also presented for these heteroleptic systems, and comparisons are made with known values for the homoleptic parent species Cr(bpy) 3 3+ , Cr(phen) 3 3+ , and Cr(TMP) 3 3+ . Also reported is the synthesis of these three homoleptic complexes via the appropriate cis-[Cr(diimine) 2(CF 3SO 3) 2]CF 3SO 3 precursor species. The procedure is an attractive alternative to the widely employed literature method for homoleptic systems involving the preliminary formation of air sensitive Cr(II) complexes.